'76 280Z Question on dist/manifold vacuum, dist timing, fuel pressure, brake booster

[FastWoman]

My '82 AFM's terminals are labeled a bit differently. I belive my 8-9 measurement would be 129 ohms, and my 6-9 would be 357 ohms. The difference (6-8) would be 228 ohms. I measure 231 ohms. Close enough.

(So my '82 AFM's resistances are similar to yours, Jenny. I've never had it in a running car, so I don't know how it operates.)

Pennies vs. Voltages:

pennies V (% supply) grams

22 54.79 56

27 26.67 69

32 16.36 82

42 8.97 108

47 6.55 120

52 5.45 133

57 4.85 146

62 4.24 159

67 3.27 172

72 2.91 184

77 2.74 197

87 2.30 223

97 1.89 248

107 1.58 274

117 1.37 300

127 1.30 325

152 1.25 389

177 1.20 453

202 1.16 517

227 1.14 581

252 1.09 645

[FastWoman]

Obviously I had some slightly sticky flap issues. Perhaps I should have hosed the working parts down with WD-40 first. I did try to shake the AFM a bit before each measurement to get the vane position to stabilize.

[FastWoman]

Jenny, the problem is that all this info is proprietary and therefore reverse-engineered, just like we're doing here.

You're not going to be able to see underneath your intake well enough to find leaks. Honestly, my yogurt cup test is the way to go. It's VERY fast and easy. It will take you no more than 5 min after you've got your AFM off.

If you've got afterfire, then it does sound like you're running rich. That wouldn't be a vacuum leak issue. You should check the CTS resistance at the ECU plug to make certain you don't have a bad connection or corroded wire somewhere. You might have a broken solder joint in the ECU. You might try picking up a spare on Ebay to try out. ZTrain had this problem and fixed his ECU by re-flowing the internal solder joints. That's just the process of melting all the solder connections, one by one, with a soldering iron. It's a bit tedious, but it might pay off for you. Another problem spot could be the cold start valve. Mine was stuck partially open, thus enriching my mixture. Obviously also check the thermotime switch.

Dinner!

[Zed Head]

I hope we don't get banned for what's going on here...

FW, if you could run the 28 quarters, we could see if an 82 AFM has the same spring tension as a 78 AFM. Or at least the equivalent weight in pennies. It appears that you have a balance of some kind.

It looks like the AFM is designed to simply split the input voltage in half, then scale it to full potential on one side of the potentiometer and zero on the other as the vane travels from closed to full open. The ECU uses one of those voltages for its injector time calculations.

Also, you can see from your chart how you lose the leverage as the vane drops past perpendicular. Each new penny has less effect. Were you tilting the AFM to avoid the rubbing or not?

[Zed Head]

I ran 50 pennies, using 24 lb paper, and 5 staples.

Battery voltage was 9.33 to start (colder in the garage).

I got 0.68 volts out or 7.3%. Close to yours but with the heavier paper and more staples, should have been a lower output.

It would be nice to see what a "bad" one reads. I sent mine to MSA for the core.

[FastWoman]

Hey Zed,

No, I didn't change the tilt. There's not any significant dragging of the string, at least in an '82 AFM. I do note some minor differences in relation to the '78 -- no backfire relief valve, a slightly different stop for the vane (full closed), and a somewhat different configuration of air bypass, with two idle mix adjustment screws, rather than the one. Anyway, yes, there's definitely a leverage issue. I considered tilting the meter but thought it would be better to aim for easy repeatability, hence the huge pile of pennies.

Yes, I do have a centigram electronic scale.

The average weight of 3 quarters is 5.66g (each). Therefore 28 quarters would be approx 158 g -- roughly equivalent to 62 pennies, yielding 4.24% of the supply voltage, vs. your 5.1%. (All things considered, that's actually pretty close. Remember that my vane drags/sticks just a bit.)

I get 41 pennies at mid-vane, not 62 (not counting the 2 pennies worth of weight in the paper). I'm considering mid-vane to be the point at which the wiper is evenly aligned with the silver contact arm.

Do you get 22 pennies to just start opening the vane? I think that might be the source of the differences in our measurements.

FAIW, the Atlantic Z beer can method is based on measurements from a '76Z and an '80ZX. My '82ZX looks just like the '80ZX pictured in the writeup. According to the author, the spring tensions are the same. Perhaps my AFM is off. Mine seems not to have been readjusted, but the cover was conspicuously loose when I got it. I don't know its history or how well it works on an actual engine. All I know is that I got it cheap.

Edited February 19, 2011 by FastWoman

[Jennys280Z]

What the heck? I've got three rusty washers, a locking washer, and what looks like a ground wire coming off of the "water temperature switch". Why are these iron washers on here? I hope this isn't going to be a horror story like my alternator where some mechanic broke the bolt off and then just jammed another bolt in there (now too long for the hole, hence the washers).

The FSM just shows a bolt head there with one washer at most. Putting these washers on here has not only caused considerable rust but it's made the bolt head almost inaccessible as it's going right under the fuel rail, getting close to the distributor, there's no way I can even get a pinky underneath it to catch it when I pull it out. I don't even know for sure what this thing is...it looks smooth like a sensor but it might just be an unthreaded bolt. I got the thing loose by using the open end of a wrench from the top but I don't know how to get this long bolt and all these stupid washers off without it falling down into the engine bay somewhere. GRRRRRRRRRRRR

Not sure if all this corrosion could be related to any of my issues???

The FSM told me to take my upper radiator hose off to get to the CTS. It doesn't look very helpful to take the hose off however. I can't figure out how to get a wrench in there.

...do you guys think that this rust is an issue or should I just retighten it and not worry?

Edited February 20, 2011 by Jennys280Z

[Jennys280Z]

There's rust on both sides of the ground wire including the surface of the engine housing. I get paranoid about stuff like this. Could this resistivity on this switch cause runnability issues?

[Zed Head]

That is a ground wire. The switch just completes the ground when the engine is cold. The thermotime switch only works to shut off power to the CSV when the engine gets warm or when it gets hot from usage. It would only affect starting.

You probably have a four port housing, but since you don't have the water temperature switch for the extra pickup coil (1976 Federal, like I have) they just put a plug in the extra port.

That does look like a tight fit. I had mine off to do some manifold work when I put a new one in so can't tell you how to get in there when it's on the engine. Good luck.

[Jennys280Z]

That is a ground wire. The switch just completes the ground when the engine is cold. The thermotime switch only works to shut off power to the CSV when the engine gets warm or when it gets hot from usage. It would only affect starting.

You probably have a four port housing, but since you don't have the water temperature switch for the extra pickup coil (1976 Federal, like I have) they just put a plug in the extra port.

That does look like a tight fit. I had mine off to do some manifold work when I put a new one in so can't tell you how to get in there when it's on the engine. Good luck.

Thanks Zed I'm just going to buy a 19mm deep socket at Autozone. I need a 1/2-to3/8 adapter anyway so it's tool time again.\

I answered my own question when I tried to pull the bolt all the way out the head butted into the fuel rail. I don't even want to take it off now so I'll just clean it as best I can where it is. xx

[FastWoman]

Jenny, I think that rusty bolt with the washers and the one opposite it secure the thermostat housing to the cylinder head. As you deduced, the washers are there because the bolt is too long. The hazard of having that rusty bolt insert too far is that it will actually push on the back of the timing chain guide and bend it, causing problems you don't even want to think about. You can see the backside of this threaded hole if you remove your valve cover.

If I were you, I'd first remove the thermostat housing cover via the two bolts on top and then the thermostat housing via the two bolts on the side. then you can replace the sensor and put everything back. The reason I recommend taking all this apart is that it will be corroded. The longer it corrodes, the harder the bolts will be to remove. The bolts probably need freshening, and the threaded holes should be chased out with a tap. (Note, watch the aforementioned threaded hole very carefully with the valve cover removed as you chase the threads out, so that you don't damage the timing chain guide.) This is also a great opportunity to get a fresh gasket between the thermo housing and head. Seepage there can cause you big headaches later.

Be careful, because of the corrosion. Use lots of PBlaster. Reassemble with plenty of antisieze. Check my "purs like a kitten" thread for a recommendation by ZTrain to place studs in the thermo housing for the cover. I did that, and it worked great.

If your bolts don't turn with reasonable force, don't get heroic. It might not be worth the fight (and the broken bolts). Just go for the coolant temp sensor by itself. It will be hard to access, but it probably won't be screwed in too tight.

[Jennys280Z]

Well I bought a $7 19mm deep socket from Autozone and it made removing the CTS a snap. Now my problem is, the Beck Arnley CTS I got from Rockauto doesn't fit. The electrical connector on my car has three nubs that lock the connector on via the clip and my connector's nub is in the middle of the side. The nub on this Beck Arnley sensor is offset from the center. Now what. I don't know what their return policies are...anyway I bought the $12.65 one for a '76 280Z. Beck Arnley part # 1580134. To be clear, it fits on the housing but not the connector. Buyer beware.

I'm so frustrated at this point I'm about ready to sand down or cut off the extra material on the connector that's sticking out in the wrong place, and then install it with only 2/3 of the usual lockdown.

Looking up rockauto's return policies now...they'll probably say that if I bought their new plug and connector, it would fit fine with this part.

Beck Arnley has another CTS for my car that's like $27. Is THAT the one that actually FITS? GRR